1. Field of the Invention
The present invention relates to a data shuffling method for shuffling data having a predetermined arrangement such as video data for which interpolation of data error is possible by using the adjoining data and to an apparatus for the same.
2. Description of the Related Art
In most cases, the data of pixels constituting a video signal have some correlation with the adjoining pixel data. Even in a case where a data error is generated in the data of a predetermined pixel, the data error can be concealed by using the data of the pixels on the periphery thereof. On the other hand, data error caused during the transmission of video data frequently occurs due to noise etc. and it is a rare case that the data error is uniformly distributed in the entire video data during the transmission. The data error is frequently concentrated at a specific position. For this reason, when transmitting video data, signal processing referred to as "shuffling" is carried out so that the data error generated during the transmission and concentrated at a specific position is not concentrated at any specific region of the original video.
The shuffling is processing wherein the arrangement of the data of the pixels constituting the original video signal is changed so that the adjoining pixel data are not together affected by noise etc. and the data of adjoining pixels in the original video are spaced away from each other at a predetermined interval in the transmission frame used for the transmission.
In the shuffling processing, for example when the pixel data are stored in a memory circuit in the original order and the stored video data are read, the pixel data are read in an order which is preliminarily set in a ROM table and differs from the original order. By changing the order, the adjoining pixel data are dispersed in the memory circuit.
Heretofore, there has not been known any system or apparatus for performing transmission after shuffling the video data.
In cases other than a transmission system, for example, a D2 type video tape recorder or the like performs the shuffling by dividing the video data for every 85 lines in the case of the NTSC system when recording the video data on a video tape.
Due to the relation of the recording format etc., however, the shuffling must be carried out while dividing one field into three segments and one line and 445 samples' worth of dummy data is added to the last segment. For this reason, if this system is used for transmission, there is a large waste in transmission. Therefore, it is difficult to adopt this system as the shuffling method at the time of transmission.
Further, at the present time, a communication line of an asynchronous transmission mode (ATM system) has been put into practical use. Studies are being made on the transmission of video data via a communication line of the ATM system. When the communication lines of this ATM system stretch out over the entire world, it is expected that the quality of the communication lines will greatly differ depending upon the area or distance.
For this reason, it is expected that there will be cases where the method of the shuffling processing must be changed in accordance with the quality of the communication line. That is, where the data error rate of a communication line is sufficiently low, it is expected that the delay time in processing will be regarded as more important than the error correcting capability and shuffling processing which has a short processing delay and is simple will be carried out, while where the data error rate of the communication line is high, the error correcting capability will be regarded as more important than the delay time in processing and the need will arise for performing shuffling which has a long processing delay and is complex.
According to the method using a ROM table as mentioned above, however, it becomes necessary to change the content of the ROM table whenever the method of the shuffling processing is changed, therefore the change of the method of the shuffling processing in accordance with the quality of the communication line is difficult.
On the other hand, where the same shuffling processing is carried out with respect to communication lines having a greatly different data error rate as mentioned above, it is expected that the data error generated in the video data will not be able to be completely concealed and that the quality of the video after the reproduction will be lowered. Further, conversely, irrespective of the fact that the transmission can be carried out via a communication line having a sufficiently small data error rate, it is expected that a large transmission delay will be uselessly induced by the shuffling processing.